Through-bond and through-space coupling in photoinduced electron and energy transfer: An ab initio and semiempirical study

Ab initio and semiempirical calculations of transfer integrals for electron transfer and energy transfer have been carried out on rigidly linked norbornane-bridged naphthalene dimers to gain insight into the relative importance of through-bond and through-space interactions on photoinduced energy and electron transfer processes. In the absence of direct through-space orbital overlap between the naphthalene moieties, through-bond interaction involving the linking polynorbornane bridge is found to significantly enhance the transfer integrals for electron transfer and triplet-triplet energy transfer. For singlet-singlet energy transfer direct through-space Coulombic interaction between the naphthalene moieties is non-negligible at the separations considered and acts to reinforce the through-bond interaction. The relationship between electron and energy transfer processes and the application of these results to the interpretation of recent experimental data are discussed.